Iron ore review 1990-1998

Mineração

Iron ore review 1990-1998

Wilson Trigueiro de Sousa

Mineral Engineering Graduate Program

Federal University at Ouro Preto-UFOP, Brazil

E-mail: [e-mail]

Luiz Henrique de Campos Merschmann

COPPE Graduate Program

Federal University at Rio de Janeiro-UFRJ, Brazil

E-mail: [e-mail]

José Thomaz Gama da Silva

Mineral Engineering Graduate Program

Federal University at Ouro Preto-UFOP, Brazil

E-mail: [e-mail]

Resumo

Uma das maiores reservas de minério de ferro do mundo está localizada no Brasil. O país é um dos mais importantes produtores e exportadores de minério de ferro, contando com minas modernas, uma malha eficiente de ferrovias e portos, além de mão-de-obra mineira qualificada. Um estudo engolobando aspectos gerais do minério de ferro é a seguir apresentado: definições, geologia, recursos e reservas mundiais, especificações granulométricas, lavra, tratamento, transporte e uma análise do mercado mundial na década de 1990.

Palavras-chave: minério de ferro, lavra, transporte transoceânico.

Abstract

One of the world's largest iron-ore reserves lies in Brazil. The country is a major iron-ore producer and exporter due to modern mines, an efficient railway and port network and skilled mining personnel. A review of this reality is presented in this paper. This review considers the general aspects of iron ore, such as definitions, geology, world resources and reserves, ore size specifications, mining, ore treatment and transport. Moreover, it summarizes the worldwide iron ore market in the 1990's.

Keywords: iron ore, mining, transoceanic ore transportation.

1. Definitions

The iron occurs as oxides, carbonates, sulfides and silicates. Commercially, oxides are more important. The main minerals that contain iron are:

• Magnetite: Fe

  ₃O

  ₄, with 72,4% of iron content.

• Hematite: Fe

  ₂O

  ₃, with 69,9% of iron content.

• Siderite: FeCO

  ₃, with 42,8% of iron content.

• Limonite and Goethite: Fe

  ₂O

  ₃

  .H

  ₂O, with 62,9% of iron content.

• Pyrite: FeS

  ₂, with 46,5% of iron content.

Magnetite, in spite of housing the largest percentage of iron, has little market value, while hematite, which contains a smaller percentage of iron, is more widely used. Limonite, siderite and other iron minerals have little application because of their small iron grade.

2. Iron geology

Stratiform deposits make up the largest part of iron deposits in the world. They are divided into three principal types: Algoma, Superior and Minette. This characterization corresponds to the place where they were first defined.

Many other types of deposits, in spite of being locally important, cannot be compared with the Superior-type deposits on a world scale. Superior-type deposits are found in Lake Superior (USA and Canada), Labrador (Canada), the Krivoy Rog district (former Soviet Union), Hammersley Range and Iron Knob (Australia). Minette-type deposits are found in eastern USA, Europe (England, France and Spain), China and Kerch (former Soviet Union). The main Algoma-type deposits occur in Ontario (Canada). Volcanic-type deposits can be located in western USA (Iron Springs and Mt. Eagle), Sweden (Kirunavara, Svapavara and Gallivare), Australia (Savage River) and the former Soviet Union (Magnitogorski).

In Brazil, the largest deposits of iron ore are located in the Quadrilátero Ferrífero, State of Minas Gerais. They are Superior-type deposits, and were originated in the early Proterozoic Age. There are significant Superior-type deposits in the Carajás region (South of Pará State) and in the Corumbá region (State of Mato Grosso do Sul). Algoma-type deposits in Minas Gerais are close to cities of Ganhães, Nova Era and Ipatinga.

In Brazil's major iron ore producing districts, the iron formation description is as follows:

• In the Quadrilátero Ferrífero, the beds are metamorphic rocks of the Minas Group (containing the Caraça Group, Itabira Group and the Piracicaba Group, from bottom to top).

• In Mato Grosso do Sul, the ore beds of the Urucum formation are 300 meters thick.

• In Marabá, Pará, the iron ore deposits of the Carajás Metallogenetic Province, are associated with plateaus. The ferriferous sequence differs from those of other ferriferous districts, and occurs only in facies oxides (itabirite) associated with two sequences of basic volcanic rocks. The sequence chemical-volcanic, called Grão Pará Group, lies directly on the basement. There are at least 200 meters of thick inferior basic rock, 250 meters of itabirite and 200 meters of superior basic rock.

3. Reserves of Iron Ore in the World

World resources of iron ore are estimated to exceed 800 billion metric tons, of which 306 billion metric tons are measured and indicated reserves. Brazil contains 6.4% of the world's reserves and is among the top six countries that retain large iron ore reserves. Table 1 shows the world's iron ore reserves in 1998.

Table 1
- Iron ore world reserves in 1998.

4. Size specifications

About 97% of the iron consumption in the Brazil is used for pig iron manufacture, 2% is used for sponge iron manufacture and 1% for the manufacture of other commodities such as cement, heavy medium material, etc. Table 2 shows the consumption of iron ore in Brazil in the period 1986-2000.

Table 2
- Iron ore consumption in Brazil 1986-2000 Unit:10³t

Table 3 - Size iron ore specifications.

Particle size is a very important variable in the iron ore trade. The main types of iron ore shipped in international trade consist mostly of:

• lump ore: particles 1/4 inch or larger,

• sinter feed: fines larger than 100 mesh,

• pellet feed: fines smaller than 100 mesh.

Direct shipping ore is bulk ore which is marketed without processing or with minimal processing, such as crushing and screening. Fine concentrates or natural ore are agglomerated to facilitate transportation and smelting. The main agglomerating processes used are sintering and pelletizing, when the iron ore consists of particles less than 1/4 inch in size.

Agglomeration is done to improve permeability of the furnace burden and to prevent loss of fines up the stack. The particles between 1/4 inch and 100 mesh are sintered. In most countries, sinter is the main feed to blast furnaces, with high performance. The sintering is an important process because it uses fine ores that had previously no economic value. Pelletizing is a process made with finely ground concentrate.

5. Iron-ore mining, treatment and transport

Iron ore passes through a treatment stage to increase its iron content and to decrease the content of impurities, according to necessity. The processing grade depends on deposit types and economic considerations. High-grade ores are treated to obtain uniform sized products, to eliminate fines and mainly to reduce impurities. Low-grade ores are treated to obtain concentrates that can compete in the market with high-grade ores.

The liberation of valuable minerals from their waste gangue minerals is necessary for the treatment of the ore. First of all, the ore is submitted to a size reduction operation (comminution - crushing and grinding). Due to the high cost of the reducing operation (grinding is often the greatest energy consumer), the grinding process must be controlled. Excess is avoided by using size separation (screening, hydraulic classifiers). Once the ore's mineral liberation has been performed, it can be submitted to separation processes, which through the simplest procedure, results in a concentrate and a waste.

The concentration operations consist of physically separating the grains of valuable minerals from the gangue minerals. The most important physical methods for ore concentration are:

1. Separation that depends on optical and radioactive properties.

2. Separation that uses specific gravity differences.

3. Separation that applies the difference of surface properties of the minerals.

4. Separation that depends on magnetic properties.

5. Separation that applies electrical conductivity properties.

With few exceptions, most mineral-separation processes involve the use of substantial quantities of water. The final concentrate has to be separated from a pulp in which the water/solid ratio may be high.

Dewatering or solid-liquid separation produces a relatively dry concentrate for shipment, which may require thermal drying to produce the final product of about 95% solid by weight.

An example of treatment is diagrammed in Figure 1.

Figure 1
- Simplified flow-sheet of the iron ore treatment in Carajás - Brazil.

About 85% of the world's iron ore production is obtained from open pit mines and the rest comes from underground mines. The mining method depends on ore body accessibility, ore size and deposit shape.

The transportation system represents the main component in the price of iron ore. Thus, most of mines use the mine/railway/seaport system to enable transoceanic trade.

6. A study of the 90's iron-ore market

The iron-ore market reached its top performance in 1997, surpassing even the most optimistic prospects for that year. World steel production has shown rapid expansion in the last six years, mainly in Asia, Western Europe and North America, accompanying consumption increase.

For the first time the iron ore production achieved the 900 Mt level. World exports reached the level of over 470 Mt.

As a consequence of steel demand changes, world iron ore production decreased an estimated -1.8% in 1998 as compared to its record high in 1997. To achieve the 1997 goal, increased production capacity and better utilization of existing technology was employed. After a decrease in 1991 and 1992, world iron ore output amassed an expansion of 12% in the following three years.

The largest production gains remained with countries that consume most of their domestic production (USA, Russian Federation and China) and in those whose exports largely exceed domestic consumption (Brazil, Australia and Venezuela).

Brazil maintained the position of the largest producer of marketable ore. China, in spite of being a large producer, has low-grade ore and is thus unable to compete significantly in the international market.

A large part of the increase in the Brazilian output was due to the additional production of CVRD's Carajás mine. In Australia the increase in the output was basically due to the expansion of BHP's Yandi mine. The expansion of iron-ore production in Brazil and Australia caused a significant increase in exports.

The Chinese output of iron ore increased to 260 Mt. in 1998. This additional production was intended for export. In India, iron ore output continued increasing and reached 70 Mt. This was obtained through the optimization of the operation in existing mines. Due to political modifications in the former Soviet Union, the Russian iron-ore output decreased. This situation was finally reversed in 1995 and dropped again in the following years. In the USA, the operational speed of the steel industry caused an increase in iron-ore mine production capacity. Swedish iron ore output rose by 8% in the mid-decade, attaining historical levels in the decade's second half, due to pellet-output growth. South Africa did not have significant production increase.

Table 4 shows the iron ore production by major producing countries from 1990 to 1998. During this period, the top four producing countries have slowly increased their share of world production. In 1990 these four countries produced 65.8% of the total world production and in 1998 they achieved only 66.2%. However, the top two countries greatly increased their share of world production, from 30.1% in 1990 to 38.1% in 1998.

Table 4
- Iron ore production by major producing countries 1990-1998.

7. Iron-ore transoceanic trade

Iron-ore trade has produced positive rates. In 1997 it achieved a new record of 472 Mt of exported ore. After the 1992 iron market crisis, transoceanic trade accumulated an increase for the next three years. The large expansion in export was caused by an increased iron-ore demand in the largest importing markets of Asia (Japan, China and Korea) and the European Union. The growth in demand was mainly due to the expansion of steel output in these markets. Japan continues being a leader in imports, accounting for more than 25% of the world's total imports, reaching the level of 120 Mt. The European Union remained as an important importation market for iron ore. Germany leads the European Union imports as the world's second iron-ore importing country. China and Korea are significant importing countries of high-grade iron ore.

Table 5 shows iron-ore imports by major importing countries from 1990 to 1998. During this period, the top four importing countries have increased their share of world imports. In 1990 these countries imported 51.5% of the total world imports and in 1998 they achieved 55.9%.

Table 5
- Iron ore imports by major importing countries 1990-1998.

Table 6 shows the iron ore exports by major exporting countries from 1990 to 1998. During this period, Brazil and Australia have, year by year, increased their share in the world market. In 1990 both countries exported 53.9% of total world exportation and in 1998 they achieved 62.6%. However, South African exports achieved the largest increase in the last few years.

Table 6
- Iron ore exports by major exporting countries 1990-1998.

The current iron ore market situation has to face low prices, over supply, reduction in demand and low crude steel production. As a consequence of this situation, measures must be taken to remain competitive. The main visible option has been the current merger processes between leading Brazilian and Australian mining companies, resulting in fewer and larger corporations.

Acknowledgments

The authors acknowledge FAPEMIG, the agency that sponsors scientific research in the State of Minas Gerais, Brazil. Its financial aid provided an important support for this study.

Artigo recebido em 27/09/2001 e aprovado em 21/12/2001.

• ANUÁRIO ESTATÍSTICO. Instituto Brasileiro de Siderurgia Rio de Janeiro, 1997.
• ANNUAL compilation of iron ore shipments by companies. Skillings' Mining Review, v. 84, n. 26, p. 4-6, July 1, 1995.
• ANNUAL Review. Metals & Minerals, p. 50-1, 1996.
• BONDI, W. As riquezas minerais do Brasil e a Organização Philips, 1985.
• QUARESMA, L.F. Ferro. Sumário Mineral, v.16, p. 50-1, 1996.
• SOUSA, G. S. A dinâmica do mercado transoceânico de minério de ferro: evolução histórica e perspectivas no ano 2000 Campinas: Geosciences Institute, Campinas State University. 1991. 150 p. (MSc. Dissertation)
• SOUSA, W. T. Substituição do aço por polímeros e compósitos na indústria automobilística do Brasil: determinantes e conseqüências para o mercado de minério de ferro São Paulo: Escola Politécnica, São Paulo University. 1995. 156 p. (PhD. Thesis).

Publication Dates

• Publication in this collection
  16 July 2002
• Date of issue
  Mar 2002

History

• Accepted
  21 Dec 2001
• Received
  27 Sept 2001